Where is Jaehaerys II?

[Emie]

We all know that there were seventeen Targaryen Kings that sat on the Iron Throne in the books, but in the show they make it seem there were sixteen. When Maester Aemon tells Jon about his family he says that Aegon V was his brother and the father of the Mad King Aerys II. When in fact, Aegon was the father of Jaehaerys II, and HE was the father of the Mad King. Even looking up the Game of Thrones Wiki site, anything about the Targaryen dynasty always shows sixteen and the lists go from Aegon V to Areys II. But what was the point in all of that? If they were trying to shorten the list to make it easier for the actor to explain his lineage, it really wasn't that much more simple. I can't imagine that it would be difficult for him to say, "yes Aegon V was my brother, and his son was Jaehaerys II, and his son was Aerys II, the Mad King." Only a few lines/words more, not that bad. 

[dariopatke]

With Willas and Garlan. But hey, we have Maegor III.

[The Fattest Leech]

I have no idea why the change for changes sake. I have had this discussion on a very small scale with someone before. To me it means one of two things: 1. HBO has already pre-fucked up any potential D&E prequels and can't make them now, or 2. HBO has already pre-fucked up and potential D&E prequels and they don't care because they will make them anyway. 

[Masha]

I think several reasons,

First Jahaerys II had such as short rule and was such an inconsequential monarch (not the good one like Aegon V the unlikely, not the horrible one like Aegon V the Unworthy, not a mad one like Aerys, and not a doomed prince like Rhaegar).

Secondly, that reddit user is right and Jon's real name is Jahaerys, so they didn't want to wear it out and make it fresh and connected at best only with Jahaerys I the Good King